Method for forming hot top liners



May 21, 1968 F. EASTWOOD METHOD FOR FORMING HOT TOP LINERS 2Sheets-Sheet 1 Filed Dec. 6, 1965 lwvaw'rorz FRED EAs-rwooD W,

A'r'rYS.

May 21, 1968 F. EASTWOOD METHOD FOR FORMING HOT TOP LINERS 2Sheets-Sheet 2 Filed Dec. 6, 1965 I N VEN roe FRED EAs'rwooD 7mm,

Wax/7 @afimm,

Arrvs.

United States Patent 3,384,149 METHOD FOR FORMING HOT TOP LINERS FredEastwood, Fairview Park, Ohio,'assignor, by mesne assignments, to FosecoTrading A.G., Graubunden, Switzerland, a company of Switzerland FiledDec. 6, 1965, Ser. No. 511,793 8 Claims. (Cl. 16433) This inventionrelates generally to the art of hot topping and, more particularly, toimproved method and apparatus for forming heat-insulating liners in aplurality of reusable hot top casings used for casting big-end-upingots.

, In the casting of metal ingots, it is common practice to use a hot topmounted on or at the top of an ingot mold for the purpose of containingfeed or head metal and maintaining it molten while the metal in theingot mold is solidifying. The metal in the hot top is above and incontact with the metal in the ingot mold so that as the metal in theingot mold shrinks, the feed metal feeds down into the ingot body andthus prevents the formation of shrinkage cavities in the body of theingot.

The latest type of hot top in commercial use for the casting ofbig-end-up ingots today comprises a single metal casing, preferably inthe form of a one-piece casting, and a heat-insulating liner on theinner surface of the casing. The 'casing itself is reusable, but theinsulating liner must be replaced after each use, i.e., after thecastingof each ingot. The liner is generally made of a relatively low costcomposition having good heat-insulating properties, the compositionbeing preformed in self-supporting slabs or sleeves shaped ,to fit theparticular casing in which they are to be used. Then after each use ofthe hot top, the remnants of the 'used liner, which usuallydisintegrates during the casting operation, are removed from the metalcasing and replaced by a new preformed liner.

When the heat-insulating liners are preformed in the shape of individualslabs, a typical relining operation consists of driving four slabs downalong the four inside walls of the casing with the slabs being wedgedagainst each other in the corners of the casing so asto urge the slabsagainst the casing walls. This method is described in more detail incopending application Ser. No. 389,656, entitled, Hot Top for Big-End-UpIngot Molds, filed Aug. 14, 1964, and assigned to the assignee of thisinvention. While this method is a vast improvement over prior hottopping methods, it is still a time-consuming operation. The reliningoperation can be carried out more efficiently when the liner'ispreformed as a single sleeve which is simply inserted in the casing,rather than a plurality of slabs (also described in the aforementionedcopending application) but the adoption of this method on any largescale requires objectionably large storage facilities for the one-piecepreformed liners. In addition, the one-piece preformed liners areconsiderably more costly to ship, It will be appreciated that theseincreased space requirements for shipping and storing the one-pieceliners are due to the large waste space inside the liner sleeves.Moreover, since the one-piece liners are generally not tapered to anysubstantial degree, it is not even possible to telescope the liners tominimize the wasted interior space. v

It is, therefore, a primary object of the present invention to providean improved hot topping method and apparatus which is extremely rapid:and which does not require any substantial storage space. Moreparticularly, it is a main object of this invention to provide animproved method and apparatus for forming heat-insulating liners in hottop casings for use on big-end-up ingot molds without time-consumingassembling operations and with 3,384,149 Patented May 21, 1968 onlyminimal shipping and storage costs. Stated another way, it is an objectof this invention to provide an improved method and apparatus forrelining reusable hot top casings in a minimum turn-around time andwithout shipping and storing bulky preformed liners.

It is another object of this invention to provide a method and apparatusof the type described above which can be carried out automatically withlittle or no manual labor. In this connection, a related object of theinvention is to provide such a method and apparatus which greatlyreduces overall hot topping costs.

A further object of the present invention is to provide an improvedmethod and apparatus for relining reusable hot top casings which permitssignificant reductions in the cost of the lining composition. A relatedobject is to provide such a hot topping method and apparatus whicheliminates the need for the heat-insulating liner composition to beself-supporting, and thus does not require any costly resin or similarexpensive binder material. Another related object is to provide such ahot topping method and apparatus in which it is not critical to remove asufficient quantity of water or other carrier liquid to render the linerself-supporting. As used herein, the term selfsupporting refers to aliner which is capable of supporting itself and being handled when it isnot engaging any supporting structure whatever.

A still further object of the invention is to provide an improved methodand apparatus for relining reusable hot top casings which eliminates theneed for a substantial resin content to prevent moisture pick-up in theliner. In this connection, a corollary object is to provide such amethod and apparatus which do not involve critical temperatures, becausetemperature critical resins are not required.

Yet another object of the invention is to provide an improved hottopping method and apparatus which eliminates losses due to breakage ofpreformed liners during shipping, storage and assembling operations.

It is a further object of the present invention to provide an improvedhot top relining method and apparatus which permits the elimination ofspring clips and other supplementary devices for retaining the liner inthe hot top casing. Thus, a related object is to provide such a methodand apparatus which obviates clip holes in the hot top casing and,therefore, eliminates the problem of metal clogging in such holes.

It is still another object of this invention to provide an improved hottopping method and apparatus of the foregoing type which permits therelining of hot top casings of different configurations without carryinga separate stock of preformed liners for each different casingconfiguration.

Other objects and advantages of the invention will become apparent fromthe following description and upon reference to the accompanyingdrawings, in which:

FIGURE 1 is a perspective view of a hot top constructed in accordancewith this invention, with one corner of the hot top being broken away toshow the internal structure.

FIG. 2 is an end view, partially in section, of a mechanism for formingthe insulating liner in the hot top of FIGURE 1; and

FIG. 3 is a side elevation, partially in mechanism of FIG. 2.

When the invention is described in connection with certain preferredembodiments, it will be understood that it is not thereby intended tolimit the invention to those embodiments. On the contrary, it isintended to cover all alternatives, modifications and equivalents as maybe included within the spirit and scope of the invention as defined bythe appended claims.

section of the Turning now to the drawings, in FIGURE 1 there is shown ahot top adapted to be mounted on the top of a big-end-up ingot mold,such as used in the formation of steel ingots for example. The hot topserves to delay the solidification of the feed metal or head metalcontained within it so that molten metal can feed downwardly into themain body portion of the metal ingot to compensate for shrinkage of theingot during cooling, thereby preventing the formation of shrinkagecavities in the final ingot. In the particular embodiment illustrated,the hot top 10 includes a one-piece outside metal casing 11, with thelower portion of the outside surface of the casing 11 beingcomplementally formed with respect to the inside walls of an ingot moldso that the lower portion of the hot top can extend down into the upperportion of the mold.

For the purpose of initially mounting the hot top on the lip of abig-end-up mold, an outwardly projecting flange 12 is formed at aboutthe midpoint of the casing so that the hot top can be set on a pluralityof wooden blocks spaced around the lip of the mold. The metal casing 11is also provided with a pair of trunnions 13 located about halfway upthe casing for use in inverting the casing, and another pair oftrunnions 14 for lifting the hot top.

In order to provide the thermal insulation required to delaysolidification of the molten metal in the hot top during the casting ofan ingot, the metal casing 11 is lined on the inside with a thin liner15 having low thermal conductivity. To provide the required thermalinsulation, the liner material preferably has a mean heat diffusivityvalue over the temperature range of C. to 1500 C. of below about 0.015centimeter-gram-second units. The term heat diffusivity is defined aswherein K is the thermal conductivity of the material, 0 is the specificheat, and p is the density. Suitable highly thermally insulatingcompositions are those described in the Davidson Patents Nos. 3,072,981and 3,123,878. The thickness of the liner can vary for differentapplications, but in general it should be between about 0.5 and about1.5 inches.

If desired, a refractory bottom ring may be secured to the lower end ofthe metal casing 11 for the purpose of preventing the creepage of moltenmetal up behind the insulating liner 15 and to protect the lower end ofthe casing 11. In the illustrative embodiment, however, the bottom ringis obviated by use of an insulating liner which wraps around the lowerend of the casing, whereby the liner itself serves the purpose of thebottom ring. However, where it is desired to use a bottom ring insteadof a wrap around-type liner, a conventional sand ring may be used andheld to the casing by means of conventional spring clips. Also, aconventional wiper strip may be fitted over the lower outside corner ofthe hot top, extending entirely around the hot top with the upper end ofthe wiper strip bent outwardly to bear against the mold wall to preventthe molten metal from rising in the gap between the hot top and themold.

As can be seen in the cross sections formed by the break away in FIGURE1, the lower inside corner of both the casing 11 and the liner 15 istapered so as to form a tapered top shoulder on the ingot. This taperedshoulder reduces overrolling during processing of the final ingot, andthus increases the yield from each ingot.

In a typical steel mill, ingots are cast in large batches, or heats.Thus, every time the ingots in a given heat are stripped from the moldsin which they are cast, an equal number of hot top casings must berelined before they can be reused in the casting of another heat ofingots. Of course, one of the necessary steps in the relining operationis removal of the residue from the previous liner; the liners usuallydisintegrate during the casting operation, but sometimes there is stilla residue of the used liner which clings to the hot top casing and mustbe removed therefrom before a new liner can be applied. This cleaningstep is not a novel feature in the method of this invention and can beaccomplished by any of the conventional cleaning means used for thispurpose.

The magnitude of the problem posed by the necessity of relining the hottop casings after each use will be readily appreciated when it isrecognized that hundreds or even thousands of ingots are cast every dayin a modern steel mill. As mentioned previously, the use of onepiecepreformed liner sleeves provides an efficient means of relining the hottop casings between uses, but the space required to ship and store thesepreformed liner sleeves has mitigated against any widespread acceptanceof such a relining method in commercial casting of big-end-up ingots,especially in the larger mills where hundreds or thousands of hot topsmust be relined daily.

In accordance with this invention, the hot top casings to be relined arecontinually transferred to a fixed lining station where a perforatedforming tool is telescoped into each casing so as to form an annularcavity between the inside walls of the casing and the outside walls ofthe forming tool. A slurry comprising finely divided refractorymaterial, a fibrous material, and a liquid carrrier is then fed into theannular cavity, the liquid carrier is withdrawn through the perforatedforming tool to build up a composite layer of the fibrous and refractorymaterials in the annular cavity, and finally the forming tool istelescoped out of the casing and the layer of fibrous and refractorymaterials so that the layer forms a liner on the inside walls of thecasing. To complete the relining operation, the casing is thentransferred from the lining station to a drying station where the greenliner formed by the forming tool is dried sufiiciently to permit thecasting of molten metal in the relined casing.

The relining method of this invention represents a significantbreakthrough in the hot topping art, permitting for the first timecomplete automation without any preforming operations whatever. Sincethe liner is completely formed in situ, the method not only can becarried out rapidly without any manual labor, but also does not requireany shipping, storage, or handling of preformed liners. In effect, theliner is both formed and stored in the casing. Furthermore, since theliner is always in supporting engagement with the casing walls onwhichit is formed, there is no need for the liner to be self-supporting.Consequently, the costly resins or other similarly expensive binderswhich are used to make the preformed liners self-supporting are nolonger required, thereby substantially reducing the raw material costsand providing a significant economic advantage over other reliningmethods. The method of this invention also permits elimination of allsupplemental retaining means, such as retaining rings and the like, tohold the liner in place because the in situ forming of the liner enablesthe use of selfretaining liner configurations.

Turning now to FIGURES 2 and 3 for a more detailed description of apreferred embodiment of the invention, a plurality of one-piece hot topcasings 11, from which the residue of the previously used liner hasalready been removed, are transported in seriatim by means of a rollerconveyor 20 to a fixed lining station including a casing table indicatedgenerally at 21. The casings 11 are inverted before they arrive at thelining station so that the wider end of the hot top opening is at thetop of the casing as it enters the lining station. The casing table 21includes a central support plate 22 which is covered with a sealinggasket 23, and both the plate 22 and the gasket 23 are large enough indiameter to overlap the edges of the casing opening. As a casing 11enters the lining station, it rides over a plurality of rollers 24 whichare mounted in vertically movable brackets 25 in a channel formed in thetable adjacent the main supporting plate 22. After the casing 11 hasreached a center position on the table 21, the rollers 24 are lowered bylowering the brackets 25 so that the casing comes torest on the sealinggasket 23 on top of the central support plate 22.

After the casing 11 has come to rest on the sealing gasket 23 bylowering of the rollers 24, the entire casing table 21 is raised intotelescoped relation with a liner forming tool 26 which is mounteddirectly above the table 21 in axial alignment therewith. Raising of thetable 2-1 is accomplished by means of a plate 27 mounted on the top endof a vertical piston rod 28 which extends downwardly into a cylinder 29connected to a suitable source of pressurized hydraulic fluid. Theforming tool 26 is complementally formed with respect to the interior ofthe hot top casing 11 so that after the casing 11 and the tool 26 havebeen moved into telescoped relationship with each other, an annularcavity is formed between the perforated outside walls of the tool 26 andthe solid inside walls of the metal casing 11. Since the tool 26 and thecasing 11 are complementally formed with respect to each other, thisannular cavity will be of substantially uniform width around the entirecircumference of the tool.

After the casing 11 and the forming tool 26 have been moved intotelescoped relationship, a slurry containing finely divided refractorymaterial, fibrous material, and a liquid carrier is fed into the annularcavity by means of a manifold assembly 30 extending around the top ofthe forming tool 26. The slurry is fed into the manifold assemblythrough a feed pipe 31 which conducts the slurry into an annularmanifold tube 32 having a plurality of inside ports 33 opening intocorresponding registering passageways 34- communicating with the annularcavity 35 between the casing 11 and the forming tool 26. In order toprevent any leakage of the slurry down along the outside walls of thecasing 11, an air filled sealing gasket 36 is mounted directly below theslurry passageways 34- for engaging the outer surface of the hot topcasing 11 as it is moved into telescoped relationship with the formingtool 26. Air is supplied to the sealing gasket 36 through a pipe 37connected to a suitable source of pressurized air.

As the slurry enters the cavity 35 from the manifold assembly 3%, theslurry flows downwardly into the cavity 35, *which is closed at thebottom by means of the sealing gasket 23 bearing against the bottom ofthe forming tool, with the carrier liquid being extracted through theperforated walls of the hollow forming tool 26 so as to build up acomposite layer of the solid fibrous and refractory material on theouter surface of the tool. The liquid extraction through the perforatedwalls of the tool 25 is effected by a pressure differential which may beachieved by several different means. For example, the slurry suppliedfrom the inlet manifold 30 is ordinarily under a certain feed pressure,and this pressure itself is sufiicient in certain cases to force thecarrier liquid from the cavity 35 through the perforated walls into theinterior of the tool 26. In addition, a vacuum may be drawn on theinside of the tool 26 so as to increase the pressure differential acrossthe perforated walls and thereby enhance the extraction of carrierliquid therethrough.

In accordance with one aspect of this invention, the liquid extractionprocess is facilitated by preheating the walls of the casing 11, beforeit enters the lining station, to a temperature above the boiling pointof the carrier liquid 50 that the liquid is vaporized as it contacts theinner walls of the casing' The resulting increase in pressure within thecavity 35, due to vaporization of the carrier liquid, tends to force thecarrier liquid inwardly through the perforated walls into the interiorof the forming tool. It will be appreciated that this preheating of thehot top casings will not usually require a separate heating step in acommercial operation, since the casings to be relined are already at anelevated temperature due to the heat absorbed from the molten metalduring the previous casting operation. Thus, in a typical commercialoperation, the casings reach a relatively high temperature during thecasting operation, but by the time a complete heat of ingots has beenstripped from the molds and the hot top casings have been cleaned of theused liner residue, the casings have usually cooled to a somewhat lowertemperature. This lower temperature is usually more than adequate tovaporize water, which is probably the most common slurry carrier liquidused in this type of operation. The upper limit on the temperature ofthe casings entering the lining station depends mainly on the charringor burning temperature of the other slurry ingredients. For example,when paper pulp is used as a fibrous ingredient in the slurry, thecasing temperature should not be above about 400 F. since temperaturesabove that level tend to char or burn the paper pulp.

It should be recognized that even though the residual heat in the hottop casings is normally adequate to provide the desired temperature inthe casings entering the lining station, it is still necessary toprovide a casing preheater in order to heat new casings or casings whichhave cooled to room temperature during a shutdown. Of course, theprocess can also be carried out without any casing preheating, but thedrying times tend to be excessive in such an operation.

As the carrier liquid is extracted through the perforated walls of theforming tool 26, the extracted liquid is collected inside the formingtool and discharged by gravity through a discharge port formed by anaperture 40 in the bottom of the forming tool 26 and registeringapertures 41 and 42 formed in the sealing gasket 23 and the centralsupport plate 22. The discharged liquid then enters an effiuent chamber43 formed in the bottom of the table 21 and then on out through a wasteline 44. While the carrier liquid is being extracted through theperforated walls of the forming tool 26, the solid fibrous andrefractory material in the slurry are directed against the outer surfaceof the forming tool, with the fibrous material quickly building up arandom mat which acts as a filter to retain the finely dividedrefractory material within the liner cavity 35 while permitting thecarrier liquid to pass through into the interior of the tool.Consequently, a composite layer of fibrous and finely divided refractorymaterial builds up around the outer surface of the forming tool 26 untilit completely fills the annular cavity 35, thereby forming a green lineron the inner surface of the hot top casing 11.

One of the significant advantages of the present invention is that theinsulating liner is formed in situ on the walls of the hot top casing,'so that there is no necessity for the liner to be self-supporting as inthe case of preformed liners for example. Consequently, the relativelycostly resins which are normally used to make the preformed linersselfsupporting can be omitted from the slurry composition used in themethod of this invention. Moreover, since the lined casings are normallyused within a matter of hours after the liner has been formed, there isno problem of moisture pick-up in the casing, and thus again there is noneed for the costly resin which is used to minimize such moisturepick-up in preformed liners. The only essential ingredients of theslurry composition, other than the carrier liquid, are a finely dividedrefractory material and a fibrous material to form the filtering mediaon the perforated walls of the forming tool and to hold the compositelayer together. The fibrous material may be either organic, such aspaper pulp, or inorganic, such as asbestos fibers, or a mixture of bothorganic and inorganic materials. A suitable refractory material issilica flour, although many other finely divided refractory materialsknown in the art may be used in the place of, or in mixture with, thesilica flour. It is generally desirable to include at least a smallportion of binder in the slurry composition, but the method of thisinvention permits the use of inexpensive binders such as wheat flour andthe like rather than the costly resins used heretofore. Also, it will berecognized that many other materials may be added to the slurrycomposition for the purpose of providing the final liner with variousproperties which may be desirable in different 7 applications. Forexample, certain exothermic materials may be included in the slurry toform an exothermic layer. Many other additives are well known to thoseskilled in the art and may be added as desired for different types ofcasting operations.

After the liner cavity 35 has been filled the composite layer of fibrousand refractory material, and sufiicient carrier liquid has beenextracted therefrom to enable the green liner to maintain its integrityon the casing walls, the forming tool and the lined casing are movedrelatively away from each other, and the casing is transferred to adrying station to dry the green liner before it is used in the castingof another ingot. In order to break the green liner loose from the outersurface of the forming tool before the tool and the casing aretelescoped away from each other, compressed air is admitted into theinterior of the forming tool 26 just before the casing table 21 isretracted away from the forming tool 26. This compressed air applies abrief burst of pressure against the inner sur face of the green liner,through the perforated walls of the tool, so as to break the green lineraway from the forming tool. Alternatively, other suitable means, such asa collapsible forming tool for example, could be used to break the lineraway from the forming tool before the tool and the casing are movedrelatively away from each other.

In order to transfer the lined casing away from the lining station afterthe table assembly 21 has been lowered to its fully retracted position,the transport rollers 24 are raised into engagement with the lower endof the hot top casing so as to raise the casing slightly off the sealinggasket 23. The casing is then transferred onto a continuation of theroller conveyor 20 which transports the casing and the green linertherein to a drying station where the green liner is dried sufiicientlyto permit the casting of molten metal in the lined casing. The dryingstation may take the form of a conventional drying oven or any othersuitable drying means. It should be pointed out here that the length ofthe drying period is considerably shortened by preheating the hot topcasings upstream of the lining station, which of course, includes theuse of residual heat in .the casings to provide the desired preheatingeffect. It should also be pointed out that the degree of drying requiredin the liners formed by the method of this invention is not as great asthe degree of drying required in preformed liners because there is nonecessity for the liners of this invention to be self-supporting sincethey are formed in situ.

In accordance with a further aspect of this invention,

the inside walls of the hot top casing are provided with a recess sothat the liner formed in situ thereon projects into the recess to form aself-retaining liner. More particularly, the combination of the casingrecess and the complementally formed liner projection serve to preventthe final liner, which often shrinks somewhat during the final dryingstep, from falling out of the casing when the casing is inverted priorto being mounted on the ingot mold. Thus, the illustrative hot topcasing 11 is provided with a pair of peripheral recesses or grooves 51and 52 extending completely around the inner surface thereof.Consequently, when the insulating liner is formed in situ as shown inFIGURE 3, the recesses 51 and 52 form a part of the annular cavity 35and thus the composite layer of refractory and fibrous material whichfills the cavity projects into these recesses 51, 52. In other words,the insulating liner is always complementally formed with .respect tothe inner surface of the hot top casing 11, and thus any recesses formedin the inner surface of the casing will be occupied by complementallyformed projections on the liner which is formed in situ. In theparticular configuration illustrated, the two grooves 51, 52 areoccupied by complementally formed ribs 53, 54 which serve to preventaxial movement of the liner within the casing. Of course, axial movementof the insulating liner within the casing is not a problem as long asthe casing remains in the inverted position shown in FIGURES 2 and 3,but the casing naturally must be inverted at some subsequent pointbefore it is mounted on top of an ingot mold, and it is then that theretaining ribs 53, 54 serve to retain the liner within the invertedcasing. It will be recognized that the recesses formed in the innersurface of the hot top casings could be provided with many otherconfigurations, and these recesses will always result in the formationof a complementally formed projection on the insulating liner so as .toretain the liner in place within the casing. For example, onealternative configuration would be the provision of a single groove inthe upper inside corner of the casing (the lower inside corner in theinverted position shown in FIGURES 2 and 3) so that a complementallyshaped flange would be formed on the resultant liner .to prevent theliner from dropping out of the casing when it is subsequently inverted.These self-retaining liner configurations have the advantage ofeliminating the need for spring clips, or other supplementary deviceswhich are nornally used to secure the liner within the casing, therebyeliminating the holes which must be formed in the hot top casing toreceive the spring clips and which tend to become clogged with metal.

An alternative embodiment of the present invention comprises forming thegreen liner on the outer surface of the forming tool before the casingand the tool are moved into telescoped relationship with each other. Inthis embodiment, the insulating liner is preliminarily formed on theperforated tool by the method described in Ednell Patent 3,066,069, orby any other suitable method. Then when the hot top casing 11 is movedinto position at the lining station and raised into telescopedrelationship with the forming tool, the green liner has already beenformed and it is simply a matter of pressing the casing against thegreen liner to complete the forming, and then blowing the green lineroff the forming tool onto the casing. The casing is then lowered awayfrom the forming tool in the same manner described above and transferredonto the drying station. This method has the advantage of permitting theuse of several forming tools at a single lining station so that a greenliner can be formed on one tool while the liner previously formed onanother tool is being transferred to a casing. Then for the next casing,the roles of the two forming tools would be reversed. In practicing thisembodiment of the present invention, the casing is raised until itpresses firmly against the green liner on the forming form so as toconform the liner to the exact shape of the casing while the liner isstill in a moldable condition. The casing is then lowered away from thegreen liner until it leaves a gap of approximately one inch. or less tofacilitate the dislodging of the green liner from the forming tool by apuif of compressed air as described above. It has been found that thegreen liner can withstand the slight impact as it is transferred fromthe forming tool to the casing, even though no binder resin is includedin the liner composition.

As can be seen from the foregoing detailed description, the presentinvention provides an improved hot topping method and apparatus whichpermits reusable hot top casings to be quickly relined without thenecessity for shipping, packing, storing, and assembling preformedliners. This, of course, results in a number of attendant economicadvantages, such as elimination of shipping, packing, and storage costs,elimination of breakage problems, and the possibility of completeautomation with no manual labor whatever. This invention also permitssignificant reductions in the cost of the lining composition by virtueof the fact that the liner does not need to be selfsupporting and,therefore, does not require any costly resin to bond the lineringredients together and/or inhibit moisture pick-up. This facilitatesformation of the liner because temperature critical resins are no longerrequired. Furthermore, this invention permits the elimination ofretainer rings because the liner can be formed in situ with aconfiguration which renders the liner selfretaining, simply by providingappropriate recesses in the inner surface of the casing being :lined.Also, wiper strips can be embedded in the liner before it has beencompletely dried thereby permitting elimination of the spring clips orother supplementary devices which are used for retaining purposes. Theinventive method also makes the dimensions of the hot top casing lesscritical because the liners which are formed in situ naturally assumethe same dimensions as the casing even though these dimensions may varysomewhat from casing to casing.

I claim as my invention:

1. The method of forming heat-insulating liners in hot top casings foruse on big-end-up ingot molds, which method comprises the steps ofcontinually advancing a plurality of the hot top casings in seriatim toa fixed lining station, inserting a perforated forming tool into eachcasing arriving at the fixed lining station so as to form an annularcavity between the inner surface of the casing and the outer surface ofthe forming tool, feeding a slurry comprising a finely dividedrefractory material, a fibrous material, and a liquid carrier into saidcavity and withdrawing the liquid carrier through the interior of theperforated forming tool so as to build up a layer of the fibrous andrefractory materials in said cavity, withdrawing the forming tool fromthe casing and the layer of fibrous and refractory materials so thatsaid layer forms a liner on the inner surface of the casing, continuallyadvancing each casing away from the lining station and drying the linertherein sufficiently to permit the casting of molten metal in the linedcasing, and mounting each casing with its dry liner on a big-end-upingot mold for the next casting operation. 3

2. A method of forming heat-insulating liners in a plurality of hot topcasings used on big-end-up ingot molds, which method comprises the stepsof cooling each casing, after it is removed from a mold and ingot, to atemperature below the burning temperature of the liner to be appliedthereto and above the boiling point of the liquid carrier used informing the liner, continually advancing a plurality of the hot topcasings in seriatim to a fixed lining station, inserting a perforatedforming tool into each casing arriving at the fixed lining station so asto form an annular cavity between the inner surface of the casing andthe outer surface of the forming tool, feeding a slurry comprising afinely divided refractory material, a fibrous material, and a liquidcarrier into said cavity and withdrawing the liquid carrier through theinterior of the perforated forming tool so as to build up a layer of thefibrous and refractory materials in said cavity, withdrawing the formingtool from the casing and the layer of fibrous and refractory materialsso that said layer forms a liner on the inner surface of the casing, andcontinually advancing each casing away from the lining station anddrying the liner therein sufficiently to permit the casting of moltenmetal in the lined casing.

3. A method of cyclically forming heat-insulating liners in a pluralityof hot top casings used for casting big-end-up ingots, which methodcomprises the steps of removing the used liner from each casing, afterit is removed from the mold and ingot after each casting operation,continually advancing a plurality of the hot top casings from which theused liners have been removed to a fixed lining station, inserting aperforated forming tool into each casing arriving at the fixed liningstation so as to form an annular cavity between the inner surface of thecasing and the outer surface of the forming tool, feeding a slurrycomprising a finely divided refractory material, a fibrous material, anda liquid carrier into said cavity and withdrawing the liquid carrierthrough the interior of the perforated forming tool so as to build up alayer of the fibrous and refractory materials in said cavity,withdrawing the forming tool from the casing and the layer of fibrousand refractory materials so that said layer forms a liner on the innersurface of the casing, continually advancing each casing away from thelining station and drying the liner therein sufficiently to permit thecasting of molten metal in the lined casing, and returning each linedhot top casing to the casting area for mounting on a big-endup ingotmold for another casting operation and subsequent cyclic repetition ofthe foregoing steps.

4. The method of forming heat-insulating liners in reusable hottopcasings for use on big-end-up ingot molds, which method comprises thesteps of continually transferring a plurality of the hot top casings inseriatim to a fixed lining station, moving each casing transferred tothe lining station into telescoped relationship with a hollow perforatedforming tool which is complementally formed with respect to the interiorof the hot top casing so as to form an annular cavity between the innersurface of the casing and the outer surface of the forming tool, feedinga slurry comprising a finely divided refractory material, a fibrousmaterial, and a liquid carrier into said cavity and withdrawing theliquid carrier through the interior of the perforated forming tool so asto build up a composite layer of the fibrous and refractory material onthe outer surface of said tool until said annular cavity is filled withthe composite layer, the inner surface of said casing being providedwith a recess whereby the composite layer projects into said recess toretain the composite layer against axial movement within the casing,moving the casing and the composite layer out of telescoped relationshipwith said forming tool so that the composite layer forms a liner on theinner surface of the casing, and continually transferring each casing solined away from the lining station and drying the liner thereinsufficiently to permit the casting of molten metal in the lined casing.

5. The method of forming heat-insulating liners in reusable hot topcasings for use on big-end-up ingot molds, which method comprises thesteps of continually transferring a plurality of the hot top casings inseriatim to a fixed lining station, moving each casing which arrives atthe lining station into telescoped relation with a hollow perforatedforming tool which is complementally formed with respect to the interiorof the hot top casing so as to form an annular cavity between the innersurface of the casing and the outer surface of the forming tool, feedinga slurry comprising a finely divided refractory material, a fibrousmaterial, and a liquid carrier into said annular cavity and withdrawingthe liquid carrier through the interior of the hollow perforated formingtool so as to build up a layer of the fibrous and refractory materialson the outer surface of said tool until the composite layer completelyfills said annular cavity, supplying compressed air into the interior ofsaid forming tool so as to break said composite layer away from theouter surface of said tool and then moving the casing and the compositelayer thereon out of telescoped relationship with said forming tool sothat said layer forms a liner on the inner surface of the casing, andcontinually transferring each casing so lined away from the liningstation and drying the liner wherein sufficiently to permit the castingof molten metal in the lined casing.

6. The method of forming heat-insulating liners in reusable hot topcasings for use on big-end-up ingot molds, which method comprises thesteps of continually transferring a plurality of the hot top casings inseriatim to a fixed lining station, providing a hollow perforatedforming tool at the fixed lining station, said forming tool beingcomplementally formed with respect to the interior of the hot topcasings, contacting the outer surface of said forming tool with a slurrycomprising a finely divided refractory material, a fibrous material, anda liquid carrier and withdrawing the liquid carrier through the interiorof the perforated forming tool so as to build up a composite layer ofthe fibrous and refractory materials on the outer surface of said tool,moving said tool with said composite layer thereon and the casing to belined into telescoped relationship with each other so as to transfersaid composite layer from the outer surface of said tool to the innersurface of said casing, moving said casing with said composite layerthereon and said tool out of telescoped relationship with each other andtransferring the resultant lined casing to a drying station, and dryingthe lined casing at said drying station sufficiently to permit thecasting of molten metal therein.

7. The method of forming heat-insulating liners in reusable hot topcasings for use on big-end-up ingot molds, which method comprises thesteps of continually transferring a plurality of the hot top casings inseriatim to a fixed lining station, providing a hollow perforatedforming tool at the fixed lining station, said forming tool beingcomplementally formed with respect to the interior of the hot topcasings, contacting the outer surface of said forming tool with a slurrycomprising a finely divided refractory material, a fibrous material, anda liquid carrier and withdrawing the liquid carrier through the interiorof the perforated forming tool so as to build up a composite layer ofthe fibrous and refractory materials on the outer surface of said tool,relatively moving said tool with said composite layer thereon and thecasing to be lined into telescoped relationship with each other,pressing the casing and the composite layer on the tool into firmengagement with each other to conform said layer to the interiorconfiguration of said casing, relatively moving the casing and theconformed composite layer slightly away from each other, and admittingcompressed air into the interior of said tool so as to transfer thecomposite layer from the tool to the casing.

8. The method of forming heat-insulating liners in reusable hot topcasings for use on big-end-up ingot molds, which method comprises thesteps of continually transferring a plurality of the hot top casings inseriatim to a fixed lining station, providing a hollow perforatedforming tool at the fixed lining station, each of said casings having atapered shoulder on the lower inside corner thereof and each casingbeing inverted so that the tapered 12 shoulder is at the top of thecasing as it arrives at the lining station, said forming tool beingcomplementally formed with respect to the inner surface of the hot topcasings, said inner surface of each casing including said taperedshoulder and the adjacent end of said casing, contacting the outersurface of said forming tool with a slurry comprising a finely dividedrefractory material, a fibrous material, and a liquid carrier andwithdrawing the liquid carrier through the interior of the perforatedforming tool so as to build up a composite layer of the fibrous andrefractory materials on the outer surface of said tool, moving said toolwith said composite layer thereon and the casing to be lined intotelescoped relationship with each other so as to transfer said compositelayer from the outer surface of said tool to the inner surface of saidcasing, moving said casing with said composite layer thereon and saidtool out of telescope relationship with each other and transferring theresultant lined casing to a drying station, and drying the lined casingat said drying station sufficiently to permit the casting of moltenmetal therein.

References Cited UNITED STATES PATENTS 1,637,532 8/1927 Oliver et al.162-220 2,366,212 1/1945 Perry 162397 2,881,680 4/1959 Spengler et al92-58 2,896,266 7/1959 Anthony 264269 2,942,319 6/1960 Anthony 164-33 X3,066,069 11/1962 Ednell 162227 3,072,981 1/1963 Davidson 249-201 X3,120,684 2/1964 Gathmann 164-33 X 3,216,069 11/1965 Anthony 16433 X J.SPENCER OVERHOLSER, Primary Examiner.

E. MAR, Assistant Examiner.

1.THE METHOD OF FORMING HEAT-INSULATING LINERS IN HOT TOP CASINGS FORUSE ON BIG-END-UP INGOT MOLDS, WHICH METHOD COMPRISES THE STEPS OFCONTINUALLY ADVANCING A PLURALITY OF THE HOT TOP CASINGS IN SERIATIM TOA FIXED LINING STATION, INSERTING A PERFORATED FORMING TOOL INTO EACHCASING ARRIVING AT THE FIXED LINING STATION SO AS TO FORM AN ANNULARCAVITY BETWEEN THE INNER SURFACE OF THE CASING AND THE OUTER SURFACE OFTHE FORMING TOOL, FEEDING A SLURRY COMPRISING A FINELY DIVIDEDREFRACTORY MATERIAL, A FIBROUS MATERIAL, AND A LIQUID CARRIER INTO SAIDCAVITY AND WITHDRAWING THE LIQUID CARRIER THROUGH THE INTERIOR OF THEPERFORATED FORMING TOOL SO AS TO BUILD UP A LAYER OF THE FIBROUS ANDREFRACTORY MATERIALS IN SAID CAVITY, WITHDRAWING THE FORMING TOOL FROMTHE CASING AND THE LAYER OF FIBROUS AND REFRACTORY MATERIALS SO THATSAID LAYER FORMS A LINER ON THE INNER SURFACE OF THE CASING, CONTINUALLYADVANCING EACH CASING AWAY FROM THE LINING STATION AND DRYING THE LINERTHEREIN SUFFICIENTLY TO PERMIT THE CASTING OF MOLTEN METAL IN THE LINEDCASING, AND MOUNTING EACH CASING WITH ITS DRY LINER ON A BIG-END-UPINGOT MOLD FOR THE NEXT CASTING OPERATION.